1. Field of the Invention
The present invention is directed toward differentials, generally, and more specifically, toward locking differentials that operatively couple a pair of axle half shafts during most driving conditions and that automatically disengage one half shaft in response to predetermined speed differentials between the axles.
2. Description of the Related Art
A differential is a component of an axle assembly and is used to couple a pair of rotating half shafts which make up a portion of the axle assembly. The differential is driven by the driveshaft via a pinion gear that meshes with a ring gear mounted to the differential. In automotive applications, the differential allows the tires mounted at either end of an axle assembly to rotate at different speeds. This becomes important, for example, when the vehicle is turning. The outer tire travels over an arc of greater distance than the inner tire. Thus, the outer tire must rotate at faster speeds than the inner tire to compensate for the greater distance travelled.
There are a number of differential mechanisms that are known in the related art for use in distributing torque between the output shafts. One such differential functions to lock the axle half shafts together during most driving conditions, while disengaging the axles during predetermined conditions, such as in response to differences in axle speed when, for example, the vehicle is turning. These devices are commonly known as “locking differentials.”
Many locking differentials include a housing that supports a pair of side gears. The side gears are splined for rotation with a pair of axle half shafts. A central driver or spider is mounted for rotation with the differential housing and drives a pair of clutch members disposed on each side of the central driver. A cam member is operatively coupled for rotation with the central driver and also includes camming teeth in meshing relationship with a portion of the driven teeth of each of the clutch members. During most driving conditions, the central driver, clutches and side gears are operatively coupled together so that the axle half shafts rotate together. In the event of a predetermined desired difference in speed between the axle half shafts, such as when the vehicle is turning, portions of the teeth on the clutch associated with the faster turning axle, ride up the cam teeth such that the clutch is moved out of engagement with the central driver. This allows the associated axle half shaft to rotate at a different speed than the other axle half shaft that is still driven by the central driver. Once the speed differential is eliminated, the clutch member is moved back to its original position allowing the drive teeth to be meshingly engaged with the driven teeth on the associated clutch member.
While locking differentials of this type have generally worked for their intended purposes, certain disadvantages remain. For example, locking differentials of the type commonly known in the art are relatively mechanically complex and this complexity adds to the cost of manufacturing the devices. In addition, the interaction between the cam teeth and a portion of the driven teeth on the clutch is less than ideal because the driven teeth function to transmit torque from the central driver as well as respond to speed differentials to ride up the surfaces of the cam teeth. The drive teeth on the central driver and the driven teeth on the clutches are usually designed to cause the teeth to remain in meshing engagement. The interaction between the portion of the driven teeth on the clutch member with the cam teeth act against these meshing forces. This results in the creation of noise and vibration during conditions when there is a speed differential between the axle half shafts.
Thus, there remains a need in the art for a locking differential that has a reduced number of components, is mechanically efficient, may be manufactured at a reduced cost, and that, at the same time, reduces the noise and vibration generated when there is a speed differential between the axle half shafts.